Two leading U.S. Senators are voicing bipartisan opposition to privatizing the nation’s air traffic control system.

They’re joined by four mayors from cities across Washington state and two Pacific Northwest congressman who expressed concerns about the privatization push last year.

The Federal Aviation Administration operation manages air traffic across the U.S. President Donald Trump reportedly favors privatization, slamming the system as “obsolete” based on the opinion of his personal pilot in a meeting with airline industry executives last month.

Any privatization move would affect Seattle-Tacoma International Airport operations more than any other of the dozens of airports across Washington state, but Sea-Tac Airport has not officially taken a position on the issue because it would not have any role in the ultimate decision, Sea-Tac spokesman Brian DeRoy said.

Senate Appropriations Committee Chairman Thad Cochran (R-Mississippi) and Vice Chairman Patrick Leahy (D-Vermont) say they’re against plans to privatize the nation’s air traffic control system because it would put the system’s assets beyond congressional oversight.